A multidisciplinary approach to the study of hepatitis C virus (HCV) will involve three investigators at different institutions who bring unique expertise and resources to this consortium effort. Major research themes include the development of cell culture systems allowing efficient propagation of HCV in cultured cells, and the identification of factors which contribute to hepatic necroinflammatory disease in patients with chronic HCV infection. In Project 1, the focus will be on development of an infectious cDNA clone of HCV, positive selection of replicating HCV RNAs encoding a selectable marker protein, and rescue of a cell culture-adapted HCV. Project 2 will collaborate in the development of infectious cDNA and attempt adaption of HCV to growth in continuous cell lines by co-cultivation with infected primary chimpanzee hepatocytes. There are extensive interactions between these two projects, which also investigate viral regulatory elements in the 5' and 3' nontranslated RNA (NTR) of HCV. Project 3 will study hepatitis C infections in a well established cohort of 1356 injecting drug users and determine which viral, host, and/or environmental factors contribute to chronic liver disease. The cellular immune response to HCV infection and the clinical significance of the quasispecies evolution of HCV will be investigated. Project 3 is closely linked to Projects 1 and 2 through efforts to determine the prevalence and significance of seronegative HCV infections in humans and chimpanzees, and whether the translation initiation activity of the 5'NTR correlates with virus load or liver disease. Projects 1 and 2 will collaborate with an external consultant in pilot studies aimed at determining crystallographic structures of the HCV capsid protein and 5'NTR. Research activities will be coordinated through an Administrative Core, with a development fund reserved for short-term support of innovative pilot studies of pathogenesis and methods of control of hepatitis C.